Battery question

[Ken Honeycutt]

I thought I was pretty knowledgeable about batteries but now I'm wondering. I have 2 8D batteries on my Hunter. These are supposedly new dealer installed batteries (one year). Last summer I made the mistake of running down my #2 battery by leaving the refrig on for several days (I'm on a mooring) not realizing that I hadn't turned the frig off (I know, should have turned the battery selector to OFF). Anyhow, I ran the engine several times for extended periods before the end of the season plus during the off season I went to the storage yard and plugged the AC power in to run the charger for awhile to refresh the batteries. Long story short is - the number 2 battery doesn't seem to want to hold a charge above 11 volts. Has me concerned that I may have destroyed the battery but I really can't see how one deep discharge could cause this type of damage. The fluid level looks good, haven't taken a hydrometer test yet. I'm going to try and put a 24 hour charge this coming weekend to see if that does any good. Any other suggestions? I hate to have to shell out $300 for a new battery, plus it's a PITA to remove and reinstall.

 

[Stu Jackson]

What kind of charger and what kind of alternator

do you have? Unless you have quality three stage chargers, you may not have recharged properly. See Ample Power Primer at www.amplepower.com and West Marine's Advisor's "What Batteries Need" for proper charging requirements for batteries.

 

[sailaway78]

Deep discharge

Sometimes if you run them down far enough, there is no recovery. After Katrina, my house bank was ruined. Had a wind generator that the mast on it broke, put the wind gen in the water. Long story but ended up with basically a dead short for two months. House bank would never recover. Sorry to say, but if you have run them down far enough for long enough, I see a new battery in your future.

 

[Stu Jackson]

Many good battery chargers can

bring back "dead" batteries. We ran ours down once because the hose clamp on the bilge pump hose broke and the pump ran for days. Batteries down to 10.5 V. Recharged and they still work. Do some more homework on battery charging, you may not have to replace them. As you suggested, the hydrometer test would be a big help in finding out what you may still have.

 

[GuyT]

Try an equalize cycle for 24 hours

Nice N Easy is correct - some never recover because of the amount of hydration that occured.ALL devices connected to a battery should have a LVD (Low Voltage Disconnect) circuit that disconnects or stops current draw from the battery when the battery gets below 10.5 VDC.If your fridge did not have this protection circuit, you may have drained your battery to nothing. This is when Hydration occurs.If your fridge did have a LVD circuit, then it may recover with a long equalize. I would let it equalize for 24 hours. You'll need to add water after the equalize cycle so make sure it has enough water before you begin.

 

[Capn Dave]

Actually Guy T means

Sulfate not hydrate. Sometimes they do come back. The bad news is it ain't never gonna be like it was, when new.Fair WindsCap'n Dave

 

[GuyT]

I wrote what I meant Capn Dave

Dont put words in my mouth - The admiral does a pretty good job at that already Normally the battery solution is acid, when it gets completely discharged, its basically water. Now, lead can be hydrated into the water.If the battery had a clear case, you would see a "bath tub ring".Hydrated batteries do not usually recover - they are scrap.

 

[Ross]

Here is an interesting page that addresses the problem of very dead batteries

http://www.patentstorm.us/patents/5963008.html

 

[Ken Honeycutt]

Had to check the charger specs

This is an OEM charger that Hunter supplies. It's a protech 4 stage 30 amp charger. The way the manual describes is that it has a fast charge cycle, absorbtion charge (which I assume is an equalizer stage since it is timed), and then float stage. The 4th stage is just a fast charge cycle if the battery gets below a certain voltage while under load. I'm hoping that if I leave the charger on for 24 hours it will replenish the battery enough with the fast charge and absorbtion stage to at least get me through the summer if I keep the discharges to a minimum. I haven't run the charger more than 8 to 12 hours at the most because I don't have access to 120Volts except with my Honda (don't like to run it when I'm away from the boat or sleeping) .I saw a post earlier (I was limited to my crackberry on the road ,looks like the post was deleted) asking what my alternator was rated for. I think it is probably somewhere in the neighborhood of 90 amps but wouldn't swear to it (Yanmar YM3**). I appreciate the advice from all.

 

[Ken Honeycutt]

Stu, just saw your 1st reply

It was your post I was anwering the question about the alternator. I've been looking at that crackberry screen too long.

 

[Cap'n Ron]

CAptain Rifkin, best I know of....

Batteries have an "Amp-Hr" rating. The industry standard is to givethis number at the 20hr rate. This means that a battery with a 100amp-hr capacity can provide a continuous 5Amp discharge for 20hours. Itcannot maintain 100amps for an hour. It can probably maintain one ampfor more than 100hrs. As you see, it all depends on the rate ofdischarge. The higher the discharge, the less number of amp-hrs canbe realized. So, we need to know the amp-hr ratings of the batteries (batteries inparallel add their amp-hr rates to get a bank total). ABYC recommends in the electrical courses that a battery charger neednot have an output capacity of more than about 25-35% of the amp-hrcapacity of the banks it is charging. In general, the industryrecommendation for an off the shelf charger is that it should notcharge greater than the C/5 rate (meaning the amp-hr capacity of thebatteries divided by 5). So, in this example, a 100amp-hr bank shouldnot be charged at more than 20 amps. So, taking this information you may be able to figure out if thecharger is adequate. David-Capt. David Rifkin (USN, Ret)SAMS® AMS®ABYC Certified Corrosion, ElectricalQuality Marine Services, LLC    On Jun 3, 2008, at 9:42 PM, Greg Weeter wrote: > Hello Pokers all: I am about to install a new automatic battery> charger in> a sailboat that does not get much use. The alternator makes a fine> charge> when it runs, but since the boat sits a lot, I want the batteries to> keep> charged up.>> The charger I selected is a Guest Model 2607, 6 amp output (3 amps per> battery).>> The fine print says maximum recommended battery size for this> charger is 36> amp hours per bank. I discovered the fine print after I un-boxed it.>> The batteries in the boat are labeled as follows:>> One: 675 CCA 200 RC>> Two: 525 CCA 650 CA @ 32 degrees 23 amp average 140 minutes.>> The charger manual did not explain how to decipher the incongruous> info on> the battery labels, and I could not find an explanation in Nigel> Calder's> Book "Boat Owner's Mechanical & Electrical Manual".>> Can anyone show me how to do the math on this?>> Thanks in advance.>> > _______________________________________________